Punnet Squares

Calculate the Probability of Genetic Combinations

• can look at one trait or several
• includes notice of genotypes and phenotypes
• can be a diamond, circle, or square

2 to the Number of Traits for Number of Rows/Boxes

• Example: looking for 2 traits: 2 x 2 = 4
  • 4 rows and 4 columns

Dominant Trait is 1st

Example: If testing for blue vs brown eyes, blue eyes are recessive. Therefore B would represent brown and b would represent blue. If the parents genotypes are Bb and BB, the probabilities would come out as

• BB
• BB
• Bb
• Bb

Because B would be dominant, it comes first.

Dihybrid Cross

• looking at two genes at once ie. hair color and eye color